1. Field of the Invention
The invention relates to a method for the metallic joining of component parts which are formed of semiconductor components with metallization on a surface, metallic components or metallic substrates, as well as to a connecting (bonding) material for carrying out the method.
2. Description of the Prior Art
Such a method finds application preferably in joining semiconductor components and substrates. A large number of connecting materials, especially soft solder materials, are known, by which semiconductor components are joined to each other or to their substrates or other elements at a temperature of 180.degree. to 350.degree. C. Although soft-soldering has the substantial advantage that it has high integrability as compared to so-called pressure contacts, problems arise in power semiconductors with continuously flowing limit currents of more than 100A due to the poor alternating-load resistance of the joint. Greatly different thermal coefficients of expansion of the materials used, for instance, silicon, ceramics and copper, lead under stress to plastic deformations which generate disadvantageous structural changes in the solidified solder material. Pores and voids which can form during the solidification of the solder, especially if the partners to be joined are insufficiently wetted by the solder, accelerate the number of rejects. In addition, brittle phases which greatly reduce the strength, are formed at the boundary surfaces of the parts to be joined (for instance, copper or the metallization layers of the active semiconductor elements such as CrNiAg), due to the great supply of liquid solder (approximately 0.1 mm of solder).